Never before have so few children in the world had polio. Yet, as World Polio Day is observed Saturday, those who are trying to rid Earth of the virus say it's time to step up vaccination campaigns. If this happens, said Rotary's Carol Pandak, director of the PolioPlus program, we could have a polio-free world by 2019.

Three years ago, Nigeria, Africa's most populous country, was the reservoir of more than half of the polio cases in the world. Then the country's leaders, health workers and volunteers worked out a way to vaccinate even those children in areas where there was fighting. This year, the World Health Organization removed Nigeria from the list of polio endemic countries.

"Not having polio in Africa for 12 months is truly a great achievement," said Dr. Elias Durry, an emergency adviser for polio eradication at WHO.

History of polio eradication

The movement to wipe out polio began 30 years ago with Rotary, an international service organization that embraced polio eradication as a mission. In a Skype interview, Pandak told VOA, "We’ve made tremendous progress in our effort to eradicate polio, and it is an exciting time to be part of the effort."

"If you look at the last six months, globally, there were only 16 cases of polio," Durry said. "This is a disease that used to cripple 1,000 children a day."

Afghanistan, Pakistan

When the Global Polio Eradication Initiative was launched in 1988, the wild polio virus existed in 125 countries. Now, it exists in two.

Dr. Jay Wenger, director of the Polio Program at the Bill and Melinda Gates Foundation, said, "We’re down to one epidemiological block, the Afghanistan-Pakistan cluster. That’s the only place in the world where the wild polio virus still lives, and if we could knock it out there, we’re finished with wild polio virus."

Durry said one challenge in the region is that large numbers of people move across the borders of the two countries, so the virus can be constantly reintroduced in the communities.

In Pakistan, attacks on polio workers have horrified the world, but Durry said they had not reduced the effort to eradicate the virus. UNICEF reports that up to 98 percent of Pakistani parents want their children vaccinated, and Pandak said all polio workers now work on a local level so they are known in their communities.

"There’s truly a coordinated effort" among the polio partners, government workers and "thousands and thousands of health workers that are out there immunizing children," she said.

Other hurdles

The main challenge is to vaccinate children who are chronically missed, according to Pandak. "There’s a real focus on finding those children in those remaining pockets that have been inaccessible or are missed for whatever reason," she said.

Another challenge is complacency. When the virus disappears from a region, parents become complacent about vaccinations. Despite having enough vaccine on hand, only 14 percent of children were vaccinated this year in Ukraine.

Pandak said that in Ukraine, "the issue is convincing Ukrainian parents to have their children immunized when [the vaccine is] made available ... and also to get high-level government commitment to ensure that the response to the polio cases is [from] the highest level and done within a reasonable time frame."

The stakes are high. Sometimes the virus can gain strength when a weakened polio virus is used in the vaccine. That has happened in Ukraine, Guinea and Madagascar. As a result, the vaccine is being changed.

"If we let up with still some virus circulating in any part of the world ... the possibility of the virus to go from that place and reinfect other places in the world that have already finished is huge," Wenger said. "That can happen, and if we stop, it will happen, and then we will get polio all over the place again."

The expectations are that Pakistan and Afghanistan will be polio-free by the end of 2016. Then, if there are no new cases anywhere for at least three years, polio will be a part of history.

"We don’t want to take the pedal off the metal, as it were," Pandak said.